Complete newbie needs a little advice

[ectech]

This is my first circuit board that I am attempting to build and need a little help. Not exactly sure what is going on but maybe one of you guys could give some input. I am attaching the electrical diagram I am using. Everything thing seems to be working fine besides one thing. When I hook the positive and negative to my 12v supply D1 lights up and D2 blinks every 3.3 seconds and should have an output of 0V-.09V. When I put the positive side of my volt meter on the output and the negative side of the volt meter on my negative post I get nothing. The only time I get any reading is if I touch the negative side of the volt meter with the opposite hand I am holding the output wire on the positive side of the volt meter. Doesn't make sense to me since I have a blinking LED but a reading of 0 on my volt meter. This project is being used for an oxygen sensor simulator.
Here are the component values.
R1 100 K Ohm
R2 1 M Ohm
R3 100 K Ohm
R4 10 K Ohm
C1 4.7 uF
C2 22 uF
D1 1.7v@20mA LED
D2 1.7v@20mA LED
Any suggestions asap would be very much appreciated.
Thank You
**broken link removed**

 

[crutschow]

You will only have an output when the light blinks. Your voltmeter is likely too slow to read the short pulse of the blink. You need an oscilloscope to observe the pulse.

 

[ectech]

Thanks, I had an idea that might be it considering it's a $17 volt meter from walmart. Maybe I have something hooked up wrong to the vehicle because it does not work... As far as i know it is hooked up right but it has to be something. Not sure if anyone has any automotive knowledge that would be able to give any pointers or suggestions.

 

[crutschow]

The cost of the meter is not a factor. Expensive meters wouldn't measure the pulse either.

But you are saying the circuit doesn't work? I thought from your first post that the LED was blinking, you just couldn't measure the voltage.

 

[ectech]

I have just thought about what the problem may be. Does anyone know how much a .09v signal would drop in a wire run that was maybe about 5 ft. long? I'm wondering by the time it gets to the vehicles computer if the signal could possibly be nothing. https://www.mkiv.com/techarticles/oxygen_sensor_simulator/
This is where I originally got the information from and this person hooked it up directly at the vehicles computer. His works and mine don't so that's why I am wondering about such small voltage traveling.
Thanks

 

[ectech]

The circuit does work but it's not accomplishing what I am trying to accomplish and I am not sure why. The circuit is suppose to simulate and oxygen sensor on a vehicle which pulses signal to the vehicles ECU. The LED is blinking, sorry for the confusion. Like I said in the post before this, I am wondering if it has to do with the stretch of wire I am trying to send such small voltage through.
EDIT:
Never mind for some reason my last post isn't showing up. I have about a 5 ft run of wire for the signal to get from the circuit to my vehicles ECU. On the plans that I originally got off the internet, this guy has it hook up directly to his vehicles ECU. His works and mine doesn't.... So, I'm not sure how much that 0.9v would drop on a 5 ft wire run and if there would even be any signal left.

 

[blueroomelectronics]

Why is D1 connected in series with the power supply?

 

[ectech]

Why is D1 connected in series with the power supply?

Just to show that power is "on". If something is wrong with it I would have not the slightest clue. This is the first time I've messed with this stuff besides a class i took for a few days but mainly just learned the color coating on resistors and some basics.

 

[ectech]

What type of amperage should be coming out of the circuit being hooked up to a 12v car battery?

 

[blueroomelectronics]

D1 should simply be a rectifier diode, not a light emitting one. The 555 can only sink source about 200ma

 

[ectech]

D1 should simply be a rectifier diode, not a light emitting one. The 555 can only sink source about 200ma

So on a 5 ft, 18 awg wire there is probably nothing left for my vehicles ecu to receive then right?

 

[blueroomelectronics]

What are you trying to build? Why are you messing with the ECU?

 

[ectech]

an o2 sensor simulator, to remove my rear o2 sensors. The circuit is made to simulate the pulse an o2 sensor gives. https://www.mkiv.com/techarticles/oxygen_sensor_simulator/
This is my source, maybe you can get a little bit more understanding. If my circuit is working then the only thing I can think of that is different is how his is hooked directly to the ECU and mine is on a 5 ft run of wire.

 

[audioguru]

If the car battery is 13.8V then the voltage drop by D1 causes a supply of 12.1V to the 555 IC. The output-high of the 555 is about 10.8V and D2, R3 plus R4 cause a current of only 0.083mA in D2 which will make its blinking extremely dim.

If the ECU has a very high input resistance then the output pulse voltage of this circuit is about 0.83V.

I think that R3 should be 1k ohms and R4 should be 100 ohms. Then the current in D2 will be 8.3mA and it will be seen much brighter and the output current will be high enough to drive the ECU.

I can tell that a car has its catalytic converter removed by the stink of its exhaust. It stinks like a car from the 60ies. The stink is from the pollutant nitrogen oxide (NOX). It won't pass the emissions test. When the mechanic sees that the cat is removed then he won't do the emissions test and will rate the car as FAILED.

 

[Boncuk]

Hi ectech,

here is your corrected circuit.

Regards

Boncuk

**broken link removed**

 

[ectech]

Thanks for the help.
Audioguru: My catalytic converters are not removed... I have high flow catalytic converters on my vehicle.
Boncuk: Thanks for the diagram but that out put is way to high, I have to be pulsing no more than 1v to the ECU pin. I am not looking to drive the ECU with the circuit just replace a sensor that the ECU is monitoring.

 

[Boncuk]

Hi ectech,

has anybody given you restrictions on using a voltage divider?

 

[ectech]

Boncuk:
I have no restrictions on this, this is solely for me. Not a school project or anything so if there is a more simple way to achieve what I am trying to achieve I am wide open for suggestions. I am just pretty much illiterate on the subject of circuit boards so that's exactly why I am looking for help. I am not stuck on doing it this way I am just going by what I read on this website.
https://www.mkiv.com/techarticles/oxy...sor_simulator/
Thanks

 

[audioguru]

I recommended replacing two resistors to make the original circuit work better. Did you try it?

 

[ectech]

what type of voltage output is that going to give me by replacing those 2 resistors?